1. Suzhou Vocational University, Suzhou, China
2. School of Computer, Nanjing University of Posts and Telecommunications, Nanjing, China
3. Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, Jilin University, Changchun 130012, China
4. School of Computer Science and Technology, Soochow University, Suzhou, China
5. School of Computer, Swinburne University of Technology, Hawthorn, Australia